Vol. 9,No. 1, January 1970 where Ell and EL are the 2B1 + 2Bz and 2B1 + 2E positive hole transitions, respectively; f is the oneelectron spin-orbit coupling parameter and K is the orbital reduction factor. K I Iand K L are the principal molecular susceptibilities parallel and perpendicular to the symmetry axis of the molecule. As indicated above, there have been conflicting interpretations of the ordering and separation of the 2 B (hole ~ in d,J and 2E (hole in d,,, dyZ)states, as inferred from the electron spin resonance studies. For instance, the relative ordering of these two states as deduced recently by Harrison and Assour12 (2B2 being above the 2E) is a t variance with the earlier calculation of Kivelson and NiemanlO and also,. to some extent, with that deduced by Gibson, et aL9 However, Gibson, et al., placed these two states very close together, and their calculation was somewhat uncertain because of their failure to observe the I4Nsuperhyperfine structure which was observed by all later workers. Further, the magnitudes of Ell and EL deduced by various workers differ very widely among themselves. Roberts and Koskill have even taken the ir-ir optical transitions of the organic ring as being the d-d transitions. In Figure 1, we have plotted two theoretical curves with different Ell and EL, taking f = 500 cm-1 and K~ = 0.7. The solid curve has been drawn assuming Eli = 27,000 cm-1 and E L = 17,000 cm-I which are very close to the values deduced by Harrison and Assour. The dashed curve has been drawn taking the values of Eli and E L deduced by Kivelson and Nieman (17,000 and 25,000 cm-', respectively). The close agreement of our experimental results with the solid curve confirms the ordering of 2 B and ~ 2E states as deduced by Harrison and Assour (Le., as shown in Figure 2). The values of f and K assumed in the present calculation are in good agreement with the degree of covalency deduced from the observed I4N superhyperfine structure in this compound. For no reasonable values of f and K can our experimental data be fitted to the energy separations used by Kivelson and Nieman. This result illustrates the usefulness of the para-
+ I
Figure 2.-A
schematic representation of the electronic structure of (3-copper(I1) phthalocyanine.
NOTES 183 magnetic anisotropy in deducing the electronic structure of square-planar copper compounds. Unfortunately, neither magnetic anisotropy nor electron spin resonance can be used to locate the relative position of the 2A1 state beyond confirming that it lies higher in energy than 2B1. Acknowledgment.-We thank Drs. P. E. Fielding and A. G. McKay for providing us with the single crystals of copper phthalocyanine.
CONTRIBUTION FROM THE CHEMISTRY DEPARTMENT, POLYTECHNIC INSTITUTE OF BROOKLYN, BROOKLYN, NEWYORK 11201
Electronic Structure of C r O P in Ca2(CrO4,PO4)C1 BY C. S I M OE. , ~ BANKS,AND S. L. H O L T ~
Received Juwe 16, 1969
In the past 10 years there has been a rapidly increasing application of Wolfsberg-Helmholz type of molecular orbital calculations to the problem of electronic structure of transition metal ions.3--5 It is interesting to note, however, that while this method is widely used, the original system to which this method was applied, namely, Mn04-, has yet to have its electronic structure satisfactorily described.6-10 Indeed no small part of this problem has been the fact that until recentlyll all calculations pertaining to the MnOa- ion were based on inadequate data. The study of Cr043- was undertaken as part of a program to provide a sound experimental basis for calculations pertaining to the electronic structure of higher oxidation states. Banks, Greenblatt, and McGarvey12reported the esr spectra of Cr043--doped single crystals of Ca2P04C1 and showed that the unpaired electron is in an orbital having largely daacharacter. They also reported some unpolarized absorption spectra a t liquid nitrogen temperature showing bands a t 37,250, 27,940, 24,500, and 17,400 cm-I. These were compared to the results of Carrington, et al.,laon Mn042- and Cr043- and were shown to be similar. Extended optical measurement, however, produced important new features14 which (1) NSF-SDP postdoctoral fellow. (2) Author to whom correspondence should be addressed at the Chemistry Department, University of Wyoming, Laramie, Wyo. 82070. (3) H. Bedon, S. Horner, and S. Y . Tyree, Inovg. Chem., 3, 647 (1964). (4) F.A. Cotton and C. B. Harris, ibid., 6, 376 (1967). (5) H.Basch and H. B. Gray, ibid., 6, 639 (1967). (6) A. Viste and H . B. Gray, ibid., 3, 1113 (1964). (7) R. F.Fenske and C. C. Sweeney, ibid., 3, 1105 (1964). (8) L. Oleari, G. de Michelis, and L. deSipio, Mol. P h y s . , 10, 111 (1966). (9) P. M. Schatz, A. J. McCaffery, W. Swetaka, G. N. Henning, A. B. Ritchie, and P. J. Stephens, J . Chem. Phys., 46, 722 (1966). (IO) J. P.Dahland H . Johansen, Theoret. C h i m . Acta, 11,8 , 26 (1968). (11) S.L. Holt and C. J. Ballhausen, ibid., 7, 313 (1967). (12) E.Banks, M.Greenblatt, and B. R . McGarvey, J . Chem. Phys., 47, 3772 (1967). (13) A. Carrington and D. S. Schonland, Mol. Phys., 3, 331 (1960). (14) E. Banks, M. Greenblatt, and S. Holt, J . C h e m . Phys., 49, 1431 (1968).
184 NOTES
Inorganic Chemistry -
we report in detail. We have also included a comparison of the results of molecular orbital approximations involving transition metal ions in high oxidation states with our experimental observations. A description and critical appraisal of these theories can be found in a recent comprehensive review. l5
-
- w
m
,-
- z-
-I
-
Solid phases with the spodiosite structure, of composition Ca2XOdY, where X6+ = Cr5+or P5+ and Y - = OH-, C1-, or Br-, were first synthesized by Banks and Jaunarajs.lE Single crystals of the chlorospodiosites were grown from excess CaClz flux. Better crystals of Ca2POdC1, Cad2rOdC1, and their solid solutions were grown in the same manner by Banks, Greenblatt, and Post,'' who reported the crystal structures of the two end members of the solid solution series. The method of crystal growth was described in some detail by Kingsley, et aZ.,'* who described and interpreted the absorption and fluorescence spectra of Mn043-doped Ca2POdCl. Ca2P04Cl and Ca&rO&l possess orthorhombic crystal symmetry with four xo43-ions per unit cell.'? Each X atom is a t the center of a tetrahedron which is distorted in such a way as to have as its only symmetry element a twofold rotation axis perpendicular to the (100) crystal face. Angular distortions are such that the geometry of the molecule closely approximates D2d symmetry, however. Optical measurements and crystal face identification were made as reported in earlier publications from this laboratory.'o-22
The complete polarized spectrum of Caz [Pod,CrOe]C1,recorded a t 8OoK,is shown in Figure 1. Figure 2 shows the lowest energy band, recorded a t liquid
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